This is a paid, live course. It’s online, but it’s based in the UK, so the time may not work for you. But Lutra are the folks who make Mergin Maps.
If you’re honestly considering Mergin Maps for your org, this is the training opportunity for how all the admin backend stuff actually works.
400€ is a fair bit for a full-day training, but remember: it’s FOSS! You can install and run the system for free.