By this I mean CCleaner (file cleaner), Speccy (system temperature monitoring), and Defraggler (defragmentation).

Regarding CCleaner use PrivaZer - https://privazer.com/en/de
Regarding temps HW Monitor https://www.cpuid.com/downloads/hwmonitor/hwmonitor_1.44.exe
Regarding Defrag i personally dont see any reason why not to stick with standard win 10 defrag routine (if needing defrag at all anyway)

Hibit is well regarded on a security forum I frequent

http://www.hibitsoft.ir/Uninstaller.html

What's wrong with Piriform? I still use CCleaner... please don't tell me it's gone to the dark side.

For temps:
https://openhardwaremonitor.org/

BleachBit
GeekUninstaller
Jkdefrag

The guy above me is right BleachBit and Geek are the best

Piriform was acquired by Avast 4 years ago or so. Users reported adware in CCleaner and at one point there was hidden malware in the software. Last I knew the portable version was clean.

It's a good while that it changed owners to Avast, who added crap to it, like telemetry and popup ads.
(also, it was even hacked at some point)

Well, CCleaner and Defraggler are fine I guess, but Speccy is in pretty poor shape these days, it often gives inaccurate readings, for example it says my motherboard is 120 degrees ALWAYS, when I know for a fact it's not that hot (I've felt it).

I can only assume that is a bug, had the same reading for years (120 on the motherboard). Other than that it seemed like a decent piece of software.

That's the thing though, it's been like this forever, they keep putting out new versions but still haven't fixed this obvious bug.

CPUID's HWMonitor is pretty good.

Use HWiNFO, that's the most accurate. And if you use RTSS (Rivatuner Statistics Server), you can add an overlay in games, something like this guy explains in this video.

As for Defraggler, just stick to version 2.22.995, which is the last one since 2018. I use it too and it does the job perfectly fine (especially nowadays when almost everybody has the OS on SSDs and hard drives are used mostly for backup). And I'm saying that after using in the past professional tools like Diskeeper, DiskTrix Ultimate Defrag, or O&O Defrag.

I third the notion of Bleachbit. It does a lot more, even if the UX would scare most grandmas.

As for Speccy, I'd suggest [strike]just opening a terminal and probing the sensors with something like hwinfo or Neofetch.[/strike] I don't have any non-unix/linux suggestions here.

As for Defraggler: Just upgrade everything from rusted metal. You'll never want for defragmentation ever again. But really, this is a shrinking marketplace with limited options; maybe just stick to the Windows Disk Optimizer. Or if you can dig Unix/Linux running in a container within Windows,