Maybe I understand something incorrectly, but I’d like to avoid those hosting providers.

It's probably misleading as Cloudflare sits between a site and the Internet which allows it to speed up page delivery and, probably why it's being used here, it can help mitigate attacks on the site.

If I had to guess, the hosting of Lemmy instances probably breaks down like:

• Hetzner - Germany and Finland
• OVHcloud - France

Providers like Oracle are in there because they provide a free tier of hosting that is handy for a small instance, if you are going by numbers of users served, then Hetzner will be on top. This is at least partly down to it being difficult to find a cheaper good-quality service, which is critical if you are relying on donations.

Also I don’t get this frontend, backend thing, but apparently there’s difference when it comes to interpreting hosting providers.

Lemmy's frontend is separate from its backend, which means you can add new frontends if you want, like old.feddit.uk. I might be missing something but I don't think this will have much bearing on picking a hosting provider.

A list of links, with most active users first

🇪🇪 Estonia: https://lemm.ee/
🇩🇪🇦🇹🇨🇭 Germany, Austria and Switzerland: https://feddit.org/ and https://discuss.tchncs.de/
🇪🇺 EU-hosted: https://lemmy.zip/ (special mention to their detailed reports like this one: https://lemmy.zip/post/33065677)
🇫🇮 Finland: https://sopuli.xyz/
🇫🇷🇧🇪🇨🇭 France, Belgium, Switzerland: https://jlai.lu/
🇬🇧 UK: https://feddit.uk/
🇳🇱 Netherlands: https://feddit.nl/
🇮🇹 Italy: https://feddit.it/
🇩🇰 Denmark: https://feddit.dk/
🇵🇱 Poland: https://szmer.info/
🇸🇪 Sweden: https://feddit.nu/
🇵🇹 Portugal: https://lemmy.pt/
Catalonia and Basque country: https://lemmy.cat/ and https://lemmy.eus/
🇧🇬 Bulgaria: https://feddit.bg/
🇱🇹 Lithuania: https://group.lt/

Now about hosters themselves, you can check the sidebars. https://lemmy.zip/ for instance redirects to this link: https://www.thegreenwebfoundation.org/green-web-check/?url=lemmy.zip

Avoiding Cloudflare could be difficult, I'm not even sure which instances don't use it.

I dunno I kind of avoid thinking about stuff like this. You can stop buying McDonalds and delete your Facebook account but avoiding American servers is a world of pain.

Actually, lemmy.fediverse.observer provides information about host (you can find the whole detailed information about a chosen instance)