Going to second not using makerspace materials since they’re pretty free-for-all and the strongest 3DP materials tend to be the most prone to issues from inadequate storage like moisture.
Two top materials I’ll suggest are… actually Nylon (My favorite is Taulman Bridge) and TPU. Those are the two most common 3DP materials you’ll see that are used in BattleBots so you’ll know it’s good stuff.
Nylon has a steep learning curve and requires high-temp dryboxes I don’t think we have at the space yet (We have a couple lower-end ones laying around but I find they aren’t even close to sufficient for drying out Nylon) and warps very easily for printing- especially for a large flat adapter plate like you mention. I print Nylon at home but have to dry it out in my oven for several hours, then keep it in a drybox to keep it dry (my drybox isn’t powerful enough to dry it already-wet nylon though), and for very warp-prone prints, I need to use an enclosure too.
If you print TPU at >50% infill and a ton of walls, its surprisingly rigid. Most people are only familiar with TPU’s properties as a flexible/soft filament at low infill and walls, but TPU is extremely robust and tear resistant and has some of the strongest layer bonds in FDM printing. It’s so underrated as a material. It’s also much easier to print than Nylon, and usually much cheaper too. I’d look into TPU first.