Even better than Element? In my experience it does well with hundreds of people as well. And it allows to group channels as well, or use bots
And you can use E2EE everywhere you think you want it
I've been on IRC since its inception in the 90's and I've used ircII and BitchX etc. I'm no stranger to janky clients for communication tools.
Element is still in its death by a thousand cuts phase. There's nothing hugely wrong with it, but everything is a bit wonky. Just enough to be consistently annoying enough for me not to bother.
Summary: Matrix mostly good, Element bad. They should just copy Discord's UX 1:1, change the colour theme and work from there.
If you're managing a 100+ user channel, encryption matters fuck-all unless your invitation process is 100% airtight and every user has all their devices encrypted and locked up at all times.
Data will leak anyway so E2EE won't bring any real advantages.
Any leakage of secret knowledge shared only through these groups could be detected as treason by one of the participants in that channel. Having several channels with fewer and fewer members, closer to the party's leadership, is a typical configuration to maintain control of the most secret information.
If you only need the one channel and you need to manage a 100+ people, Telegram is by far the best tool. For "communities" Discord is a bit better, since you can split stuff to multiple channels. Anyone with basic knowledge of the internet can also install bots on both to manage dozens of different things.
Signal on the other hand is SUPER SECURE (although you will be giving your phone number to everyone), but no bots and no real ways to manage hundreds of possibly unruly people on a single channel.