I grew up playing MUDs! If you're completely unfamiliar, think of MUDs as text-based MMOs that go back almost as far as Telnet. All you really need to know is EverQuest, which was the king shit MMO before WOW changed everything, was -- by Sony's own admission -- based on Diku MUD, which was a popular code base back in the day.
dot_lvl MUD is an almost completely stock instance of the ROM 2.4 codebase. ROM is sort of the most video gamey MUD codebase; it's very combat-focused and doesn't do much to encourage roleplay. I've really never been much of a roleplayer, which is probably why I gravitated to ROM in my childhood. ROM is a really strange game by modern standards, both because WOW changed MMO design so radically and because MUDs were really chat rooms first and video games second. That means there is a lot of downtime. Back in the day, sleeping for a few ticks to restore your mana and mv wasn't so bad, because that was time you could spend shooting the shit on the gossip channel. These days, though, you're lucky if one other person is online, so all that dead time truly is dead. Eventually, I'd like to rebalance dot_lvl MUD so it's less agonizing to play in 2024, but until then, just know this is a very old video game ripped from its 1990s context and go in with tempered expectations.
With that out of the way, if you want to try it out, the easiest thing to do is grab a MUD client. My recommendation is Mudlet. You can find dot_lvl MUD at mud.dotlvl.tv port 9000 but be warned; DO NOT use a password you use anywhere else on this MUD. Your password is stored in plaintext and the connection is not secure. I will not look at your password, but you must understand that this is very old software that predates serious advances in Internet security.