I use graphene os and its great and fairly easy to install. Only works on Pixel devices though so you would have to get one of those.

The os and the apps that are built in are quite nice basically just look and feel like stock android. Beyond the built in stuff it is a bit more hit and miss if you want to stick to FOSS only like osmand is ok for maps but not really close to google maps. Personally I stick to only FOSS apps but you dont need to be as paranoid as me even while using graphene you can install apps from the play store including google apps. Graphene does have additional privacy protections when using google apps and you can take that a step further by having a separate profile for apps you dont trust. Really though you should read through some of the docs on the graphene website because only you can decide whether the convenience tradeoffs are worth it for your specific case.

To anyone reading this a 6 is a great pick but its worth knowing that the 7 year update promise only began with the pixel 8 so if you buy a 6 in 2024 it probably only has about 2 years of updates left. However they are only like $150 used I think so the value is probably there even if you only get 2 years of use out of it.

I'm not sure about over in Europe but around here the trick to an affordable Pixel is to just buy last years model since you can usually find them lightly used or even new in the $300 - $400 range and updates are only incremental anyway and since they get 7 years of updates now it should be good for quite a while.

For google play protect yeah thats a bummer, I just use my banks website but I don't know if European banks allow that.

Personally though I love Graphene OS it turned my phone from a device I hated due to anxitey I feel around corporate surveillance into a device I genuinely like again.

A few things I have observed over the years you might want to check. Take a flashlight or something and look at the actual contacts in the port and see if they are bent. Sometimes the old cheap 4 in one carts have poorly made PCBs what arent beveled correctly or are too thick and squish the pins and they no longer make good contact. It looks like an official one in the pic but unless you have had this since new who knows what someone threw in here. see here for some more info on that

Also these backup carts do just sometimes go bad though I don't know if I have ever seen an official one go bad but buying a new one to test may help with that as they aren't that expensive. They also usually have lots of built in features like an action replay and acting as an extended ram cart. Just make sure to try and check that the pcb is made correctly with that link above

Depending on your hardware you should be able to have Handbrake use your GPU to reencode the video much faster than your CPU. If you have Nvidia it would be Nvenc, Intel is Quicksync, and AMD is VCE. If you select one of those as your codec it should go much faster. Check the hardware encoders section on the Handbrake documents https://handbrake.fr/docs/en/1.4.0/technical/video-nvenc.html . Even if you were using windows you would run into the same problem at some point you are limited by how fast your hardware can process the video and no software can make up for that.