Have you seen Abdussamad's page of Electrum guides at https://bitcoinelectrum.com/? There is one for how to verify Electrum using Kleopatra (link here) which is pretty straightforward to follow and use. Hopefully it should help you out. Make sure you double check Thomas V's GPG key which appears on that page, to protect yourself in the rare chance that that site is hacked.

There is no way to contact everyone who uses, or intends to use, Electrum - there is no database of users, in-wallet messaging service, or email sign up. The best that can be done is to give clear instructions on the site, which is already done. On the landing page it says to verify the signature, and on the download page there is a box which explains why you should verify signatures, and provides links to various tutorials.

As you say, we can talk about it on the forum, but the majority of threads are ones such as this one - users who have already ignored the instructions, installed malware, lost their coins, and then come to complain. Few users seem to spend any time doing basic due diligence before downloading and install new software.