Back on the topic of Lancer.
Oh dear god, not fucking Lancer. No no no no just do yourself a favor and don't.
Community is more of a rainbow dumpster fire than D&D, PF, Battletech, and so on. There's a reason for this that I'll get to later.
Half of the Lancer content that exists is just homebrewed bullshit with official logos on it pretending to be official content with logos and shit, and it's usually wildly unbalanced(moreso than just finding someone's homebrew crap on a 5e wiki).
The setting is autisticly detailed in a good way. Even down to the economy, space ship combat, and so on. The problem is that since the players are all just mech pilots, they'll never interact with any of it.
There is almost no support for the "game" part of roleplaying game outside of the mechs. In other words, it's just talking with trying to shoehorn in a reason to even use a skill for a diceroll.
Players start at license level 0, there is next to no choice for anything till you can get some mechs as an option at license level 2. If I recall correctly the system expects around 4 combat encounters for every license level. But then the game also caps out at license level 6, so for about 1/3 of the campaign, one shot, whatever you're doing if you start at 0 your players will have next to nothing to pick from(this is why most people start at LL3 or 4).
Running the game, for whatever reason all enemy mechs are different and incompatible to what the players use even though in universe this shit is basically all made on giant 3d printers. Because of that there's also no salvage, usually no "loot"(some of their written adventures have an occasional experimental weapon or gear item drop but it's not common and they aren't amazing compared to what you can normally just pick at your current LL), and so on.
The enemy mechs are also just base model units that have modifiers, and even more modifiers and then more modifiers tacked on. Played a game at LL3, and the DM showed me an example of what he was having to parse through to determine NPC combat abilities. Most of it's just stat modifiers but it's like having 10 different yugioh cards worth of text to read to determine wtf the enemy is supposed to be capable of doing in combat.
Initiative alternates between players and DM, which can sometimes result in a canadian stand-off of people not wanting to go first, or an alternative of people wanting to take forever to determine an order because they want to get some kind of synergy going, which can drag out combats forever.
Because of the lack of individual player options at lower levels trying to find synergies with other players is basically the only way to avoid "I walk over and hit the thing with my stick". But then if someone has a chomolungma now you've got a 15 minute player turn sorting out the hacking if they use their cooldowns all at once. Kinda like the problem of someone playing a decker in shadowrun.
Lancer SHOULD have been a skirmish mech combat game. Not a fucking TTRPG. This becomes very obvious, very quickly when you realize that you're just playing on side of the table in an army, while the players are just playing as individual models in the equivalent of an army for Killteam, Infinity, etc.
On top of all of that. The game encourages just flippantly swapping out almost everything about your mech, including the mech itself so on top of not having a character that can do anything meaningful on their own, the mech isn't anything special nor is there any downside to getting it blown up. And that leads into the reason the genderspecial alphabet people love this shit because their mech is just like them, and can change to whatever whenever.
