They're not the only ones. I consider myself up to date, and I had no idea Linode was in the VPS business. If I had to guess their mission, it sounds like Tailscale. [1]
I've used Digital Ocean and all the big cloud providers. Vercel, Netlify, Heroku.
Haven't touched Akamai, but I certainly know of it.
You are probably too young to remember the php Cpanel hosts then.
Linode was one of the big names in being cheap and having an actual vps where you could do whatever. Short of actually buying a rack and the accompanying hardware/networking software (not renting and having your electric/network subsidized) having a vps is the cheapest slickest option to do whatever, part of why I have never bothered with any of the Iaas options. At least AWS blows hard-core in comparison, a lot of the alternatives focus on optimizing some use case, not doing whatever the hell you want.
I'm not sure how you would even compare tailscale, that's focused more on connecting all your boxes e.g. on linode...
Linode has been around forever and were once one of the few games in town. They were into cloud computing years even AWS was. A lot of, er, elder statesman developers remember them from way back then. So if you’ve gotten into the game less than 15 years ago, it makes sense that you may not have heard of them.
I was running websites for clients on Linode like 10 years ago. I have to check, but I’m almost certain DigitalOcean didn’t even exist back then. Linode has been in the game for a very long time.
Edit: I just checked. DigitalOcean launched their beta product in 2012. I think it took another couple years before developers started to really take them seriously.
Linode, Slicehost, MediaTemple and a few others I'm forgetting belong to a declining generation of hosting businesses that used to be popular in their hey days.
I just remembered Engine Yard. Like the others, Engine Yard is another notable one from that era that is still around (but their focus then was on RoR, IIRC).
I've used Digital Ocean and all the big cloud providers. Vercel, Netlify, Heroku.
Haven't touched Akamai, but I certainly know of it.
[1] https://pixelastic.github.io/pokemonorbigdata/