Glass breaks are something reported from labs mostly.
They technically can but not likely they will for myth busters, its an impressive feat to talk about. Pistol shrimp get demonized too for shooting hot sun bubbles but are one of the more peaceful of inverts you could have, I think nat geo really hurt their rep with their staged skunk cleaner killing when that will never actually happen.
Back on topic to glass breaks; It has happened, mainly in reused tanks through generations of wear and tear with large smashers, (we're talking 20 year old tanks with probably several generations of large smashers, most home aquariums the silicone gives out before then), the overnight cases are from small containers not made of glass.. I can personally advocate for 3 cases of N.wennerae, one of the weaker species, breaking out of kritter carriers and betta breeders (usually these are made of hard plastic) via the corners shattering, but obviously thats something I wake up to not something i put them in and expect an immediate result. Majority of the time even if you watched them they'd focus on your presence and not hit it.
The main way it happens is smasher's brains can't process the material of a hard surface so when they're burrowing, they tend to really wack at it for hours and commit to one spot. Waving your finger infront of the glass won't make it jump out and face hug you, but when they hit the same spot 50 times commiting to dig deeper, that's why there's a warning label. The solution is just laying a sheet of pexi/acrylic to the bottom of any aquarium you intend to keep a mantis in, this way when they dig a burrow and start hitting the bottom the glass is shielded from a more absorbent material. Full acrylic tanks can work too, but; they're painful to clean without scratching (not to mention cleaning is already awkward when having to quickly do it with a mantis), small thin acrylic can still crack at the seams its not bulletproof, and most importantly, cost too much. If you notice any spots they uncomfortably hit a lot, you can use something magnetic to put an acrylic shield there, considering doing the same for where my powerhead is cause my one O. scyllarus frequently hits the upper corner around it.
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As for other stuff: 20L is too small, 29 standard is what i'm using but wouldn't recommend, 40 breeder is the nice sweet spot for water quality and space. If you intend to get an O. Scyllarus (true peacock mantis) be sure to do your research on IDing them and get from a reputable source, many gotten their mantis species either unintentionally or mislabeled and a quick skim will show that's still true even this week alone, ask pictures and ID yourself before buying, especially since O. scyllarus requires more commitment in the setup alone.
Burrows are the biggest killer to large odontodactylus, U shaped burrows that are pitch black inside are necessary. Can be done with PVC but IME the most success i've had was aquacultured rock shaped like a tunnel with sand exposed, and a TON of rubble/sledge hammered rock, and frequent feedings of snails and clams to add building material naturally.
