We can trust ThomasV right?
Some people would say yes. Others would say that you shouldn't trust anyone.
Have you ever heard any electrum incidents of stolen funds in cold storage?
Such incidents have always been due to user error - generated on an internet enabled machine, seed phrase stored insecurely, etc. - and not due to an Electrum error.
As ranochigo points out, unless you review the code yourself, you are going to have to trust
someone, whether that is the developer or the community who are telling you it is safe. If you do not have the required knowledge to review the code yourself, then this is what I would do -
Download and verify Ian Coleman's site
Download and verify Electrum
Run both on a permanently airgapped machine running a clean OS
Flip a coin 256 times and enter the entropy in to Ian Coleman. It will generate a seed phrase for you
Double check your coin flips against the BIP39 wordlist in groups of 11 to make sure the seed phrase generate matches your entropy
Enter the same seed phrase in Electrum
Check that the addresses provided by both Ian Coleman and Electrum match
This allows you to ensure the entropy is random, the seed phrase matches the entropy, and the addresses match the seed phrase, all without requiring any review of the code.