Kubuntu freezing and crashing. How can I check health?

[Erich]

Sequence of what happened:
1 : Laptop froze during video call. After reboot, everything seemed to be back to normal.
2 : System broke without freezing, I was not running anything. Pressing Ctrl+Alt+F2 I got the error

systemd-journal Failed to write entry. Ignoring: read-only file system only

https://askubuntu.com/questions/1173...file-system-on
After reboot It got even worse and I got stuck into busybox.
It was solved by running fsck using a live usb.
Now : System is slow even thought CPU and memory are not even used at 50%! PC got slow by simply moving files.

It seems something is still wrong, but I don't really know the source of the problem. Is there any way to check the system health to see whether there is a problem with OS or with the hardware?

Basic info
OS: Kubuntu 20.04
KDE Plasma: 5.18.5
KDE Frameworks: 5.68.0
Qt: 5.12.8
kernel: 5.4.0-72-generic
OS: 64 bits
Processors: 8 ?— Intel® Core? i7-8550U CPU @ 1.80GHz
Memory: 15,5 GiB de RAM

From $lspci

00:00.0 Host bridge: Intel Corporation Xeon E3-1200 v6/7th Gen Core Processor Host Bridge/DRAM Registers (rev 08)
[B]00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 620 (rev 07)
[/B]00:04.0 Signal processing controller: Intel Corporation Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Thermal Subsystem (rev 08)
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
00:15.0 Signal processing controller: Intel Corporation Sunrise Point-LP Serial IO I2C Controller #0 (rev 21)
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI #1 (rev 21)
00:17.0 SATA controller: Intel Corporation Sunrise Point-LP SATA Controller [AHCI mode] (rev 21)
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #1 (rev f1)
00:1c.4 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #5 (rev f1)
00:1c.5 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port #6 (rev f1)
00:1f.0 ISA bridge: Intel Corporation Sunrise Point LPC Controller/eSPI Controller (rev 21)
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
01:00.0 3D controller: NVIDIA Corporation GP108M [GeForce MX150] (rev a1)
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)
03:00.0 Network controller: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32)

From $lscpu

Arquitecture:                     x86_64
CPU operational modes:      32-bit, 64-bit
Ordem dos bytes:                 Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
CPU(s):                          8
Lista de CPU(s) on-line:         0-7
Thread(s) per núcleo:            2
Núcleo(s) por soquete:           4
Soquete(s):                      1
Nó(s) de NUMA:                   1
ID de fornecedor:                GenuineIntel
CPU family:                  6
Model:                          142
Model name:                  Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
Step:                            10
CPU MHz:                         899.995
CPU MHz máx.:                    4000,0000
CPU MHz m?*n.:                    400,0000
BogoMIPS:                        3999.93
Virtualização:                   VT-x
cache of L1d:                    128 KiB
cache of L1i:                    128 KiB
cache of L2:                     1 MiB
cache of L3:                     8 MiB
CPU(s) de nó0 NUMA:              0-7
Vulnerability Itlb multihit:     KVM: Mitigation: Split huge pages
Vulnerability L1tf:              Mitigation; PTE Inversion; VMX conditional cache flushes, SM
                               T vulnerable
Vulnerability Mds:               Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown:          Mitigation; PTI
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and 
                               seccomp
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and __user pointer sani
                               tization
Vulnerability Spectre v2:        Mitigation; Full generic retpoline, IBPB conditional, IBRS_F
                               W, STIBP conditional, RSB filling
Vulnerability Srbds:             Mitigation; Microcode
Vulnerability Tsx async abort:   Not affected
Opções:                          fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmo
                               v pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe 
                               syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon p
                               ebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf
                                pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg 
                               fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt ts
                               c_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnow
                               prefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb s
                               tibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase t
                               sc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx sm
                               ap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm
                                ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp md_c
                               lear flush_l1d

From $sensors

[FONT=monospace][COLOR=#000000]dell_smm-virtual-0 [/COLOR]
Adapter: Virtual device 
Processor Fan:    0 RPM 
CPU:            +37.0°C   
Ambient:        +30.0°C   
SODIMM:         +34.0°C   
GPU:            +36.0°C   

coretemp-isa-0000 
Adapter: ISA adapter 
Package id 0:  +38.0°C  (high = +100.0°C, crit = +100.0°C) 
Core 0:        +36.0°C  (high = +100.0°C, crit = +100.0°C) 
Core 1:        +37.0°C  (high = +100.0°C, crit = +100.0°C) 
Core 2:        +34.0°C  (high = +100.0°C, crit = +100.0°C) 
Core 3:        +35.0°C  (high = +100.0°C, crit = +100.0°C) 

BAT0-acpi-0 
Adapter: ACPI interface 
in0:          11.60 V   
curr1:       1000.00 uA  

ath10k_hwmon-pci-0300 
Adapter: PCI adapter 
temp1:            N/A   

pch_skylake-virtual-0 
Adapter: Virtual device 
temp1:        +32.0°C   

nouveau-pci-0100 
Adapter: PCI adapter 
temp1:            N/A  (high = +95.0°C, hyst =  +3.0°C) 
                     (crit = +105.0°C, hyst =  +5.0°C) 
                     (emerg = +135.0°C, hyst =  +5.0°C) 

acpitz-acpi-0 
Adapter: ACPI interface 
temp1:        +25.0°C  (crit = +107.0°C)

[/FONT]

[jlittle]

You don't mention the obvious: Is a storage partition (that is, disk) nearly full?

I suggest running df -h in a konsole.