I use pass. Can't get more simpler than it - it's just a wrapper around gpg and your passwords/secrets are just normal plaintext files stored in a git repo. (encrypted using gpg of course) I have my gpg private key stored (encrypted symmetrically using AES) on multiple usb sticks and also have a paper copy of it tucked in somewhere secure.

I have helpful stuff for bitcoin key recovery stored in my password manager, but I don't have the keys there. The main decision when choosing the tools is whether it's for me to recover the keys by myself in future, or whether it's for my family to recover the keys when I'm gone.
I don't know about a single good solution for both of those cases, so I think it's good to think about those separately.

I use an open-sourced password manager to save some keys/mnemonics, although I feel it's not the ideal way, but what else?

Password manager for non-crypto things; I was reading your article about Tails and I was also exploring with Veracrypt.

However, I Have not decided what is the best ( and simple ) practice yet.

I use a password manager for passwords, but not for bitcoin stuff

I use Bitwarden on my phone for passwords. No bitcoin stuff tho.

I have used KeePass for the last 20 years. It works well.

I used KeePass XC for a while, but I just recently transitioned to a self-hosted version of Bitwarden. I don't store my seed phrases in the manager. I do have my Umbrel password on there, though.

On my phone yes

I use Bitwarden on my Laptop and Phone

Bitwarden, but not for seed phrases.

My rule is to never keep all the Bitcoin info in one place. My password mgr can hold a BIP39 passphrase or one key of a multi sig, but not the entire key for any wallet.