Assuming you know how to torrent(you can just get a client, I use Transmission, and click the magnet links to initiate download, but you may want to check one of the piracy comms for a more detailed guide) just search for e.g. SNES games on a torrent site like the following Pirate Bay mirror(Ad blocker recommended)

Here's one with 6666 games for a bunch of the platforms you mentioned

https://tpb.party/torrent/6988236/6666_games_Nintendo_NES-SNES-Sega-GBA-Atari-Arcade_ROMs_emulator

the actual torrent magnet link:

only 5.6GB (compressed)

this one has complete games for the platforms you listed + some more(but while torrenting you can pick and choose which parts to download, usually by right-clicking the download in your client's list and selecting something like 'files' depends on client but can be googled easily, each console will have its own folder so just untick the ones you don't need)

https://tpb.party/torrent/5712814/Dingoo_A320_Complete_ROMS_Pack_-_ROM_GBA__GBC__SNES__SMD__NeoGeo

magnet link:

27GB but will be less if you only select the platforms you want