I just got back to Half-Life, so my knowledge is kind of outdate, and I'm starting to get frustrated because lots of my Google searches lead to information that's only relevant for CS 1.6 or SRCDS while currently I'm only interested in Half-Life Deathmatch. I've already set up a vanilla HLDM server.
1. What mods to use?
When I was playing on other servers, I liked features like map voting and indications of how much time is left from the round. I'd also like HTML MOTD – not sure if there is any mod that enables it. It would be also nice if the server could recognize me as an admin and let me control it by commands (though probably an RCON password would be enough for that?). I figured that Metamod and AMX Mod X are the most prominent mods for HLDS those allow customizations via plugins. But I couldn't find a comparison to help me decide which one should I go with. For the purposes I mentioned (map voting, time left) which mods/plugins are best to use? Should I choose between Metamod and AMXX? What are the caveats of having both (if possible)?
2. Should I have bots? If so, what kind?
People are not tempted to join empty servers, but there will be no players until at least one joins, which kind of creates a chicken and egg problem. Even if someone eventually joins will disconnect soon if there is no action, they won't wait until someone else joins. I thought maybe some bots would somewhat help this, players could engage with bots until other people join. But I'm not sure about this. What kind of bots are the best to use? I remember when I was young, HPB bots were quite popular. But ~15-18 years have passed and I've been basically sleeping under a rock when it comes to HLDM. Are HPB bots still a thing? Or are there much more advanced bots nowadays to use?
3. How can I make my server more popular?
What are some (ethical) ways to make my server more appealing, so it doesn't just get buried in the list?
4. How/where do I get great maps?
I'd like to run a great variety of maps, not just the standard ones. I've been playing on a lot of servers and so downloaded lots of maps – it would be tempting to select the ones I like and put them on my server, but it's non-trivial to differentiate the assets those are possibly required by the BSP. So I thought it would be better to download maps from websites where I surely get the all the assets in one package. What are your favourite sites to download maps from? I've already Googled some, but I'm yet to find one that really has a wide variety of maps those are searchable through filters, like recommended player count, map type (rats, killbox, etc.).
5. Does HLDS support IPv6?
I'm a huge IPv6 enthusiast myself and I usually care to make my services IPv6 ready. While I enabled IPv6 access to my server, it doesn't seem to work. Half-Life always connects to it by IPv4 when I select it from the server list, and when I try to force an IPv6 connection with the "connect" console command, I get a "Bad server address" error message (tried with and without  brackets around the address, as these brackets are commonly used to denote IPv6 addresses). Is it possible to make my server dual stack, so that it can accept both IPv4 and IPv6 connections? I know it's pretty rare when somebody has an IPv6-only connection, but it would be nice to enable them to play.
6. Anything else I need to know regarding HLDS that I may not even think about? Any common mistakes that noob admins generally make?
I guess there are some newbie mistakes most people run into when they configure their first HLDS server, those might not be apparent or obvious to them. Can you share any of these?
Thanks for your insights in advance!