I am using Linux since the 90s, used Ubuntu a lot at one time, then started using MX linux, 16.1 iirc was my first install. Then I continue to use it, I have always like Xfce (coming from mwm and such), and no systemd, no snap, no flatpak etc. MX is very stable, use the latest package in .deb format. I am using it for almost 10 years now, 24/7, I am using it as my work PC too.
Windows cannot access EXT4 or BTRFS by default. Also in Linux you can use LUKS to have your partition encrypted, and Windows even with a ext4/btrfs driver will not be able to read your data.
Of course Windows, if infected, could wipe your partition table or things like this.
If you are using encryption now, you do not need to wipe the SSD, after a new install the remaining data on the "disk" will still be encrypted, without the key.
For the distro try MX Linux, they have a version for latest HW (the AHS version) and a standard version, even a 32bit one. It is based on Debian, always up to date, no complicated systemd, snap, flatpak, etc. It is using Xfce that can easily be setup with a bottom bar with menu, windows button and systray icon like Windows.
I have an IR blaster in mine (still using my PoCo F3 after 4 years, it is still pretty snappy and all) and used it from time to time but now it looks like my remote for my AV is bluetooth anyway
MX Linux (Debian based), using it for almost 10 years now (before, it was Ubuntu). Based on Debian, very stable, always up to date for every kernel/apps, use native .deb no snap no flatpak no systemd. Also it is using Xfce by default, the best DE.
True, in Canada most plan suck if you are not a heavy user. I use maybe 20 minutes of call per month, some SMS for 2FA, and quite often less than 250MB of data per month...
Old guy here too, used un*x before linux existed in the 90s. I still use a Debian based distro (MX) without systemd and no snap/flatpak/whatever. Just build/compile or install .deb and dependencies. Lastly unfortunately I had to install a flatpak to test "deskflow", the first time I installed one, I feel dirty now :-(
Have you tried MX Linux? It is based on Debian, they have a distro for RPI, and they have no systemd
https://mxlinux.org/download-links/