The frustrating thing is all the information and materials to support Samsung devices is out there, but the custom ROM development community is so ridiculously toxic and unhelpful to newcomers that few people are willing and able to mainline new devices (and supporting a new device is complicated enough that you pretty much can't get started without someone more experienced to point out the decades of cruft, pitfalls, and vendor-specific workarounds that the build processes have accumulated). More of the old guard leaves every year without enough new blood to replace them.
Search for lineage os your phone model if you're lucky someone will have ported the project to your device, the more popular it was the more likely
There are reasonable instructions
Your phone will need an unlocked bootloader, and it will not be able to be locked again while running lineage. This will prevent the use of any secure software which includes most bank apps, login authenticators. Local security is entirely bypassed by the unlocked bootloader
The problem with Samsungs is thar once unlocked, you permanently burn the knox security fuse. So, even if you re-lock it, it's not going to play nice with banking apps. It's a one-way install only. Also I'm not so sure how LOS plays with banking apps... The only one that allows full re-lock AFAIK is the Pixel (which is what I have now, after nearly a decade on Samsung).