Planes are very safe and we know how to handle hydrogen very well. It is a very common in chemical plants to have some steps including hydrogen and tanks are very well known. From a technical bases this can work. From an eviromental bases it is more difficult. Nearly all hydrogen produced today comes from cracking natural gas, which produced CO2 as a byproduct and takes a lot of energy. You can produce hydrogen using electrolysis, but the plants to do that are expensive, so the hydrogen produced that way is expensive as well. This is route easily done by train, which would be the enviromentally smart way. For small distances, to say islands or so, batteries work very well. For long distances there are some experimental hydrogen jet engines, but they are problametic. Turboprop regional planes lack the range to fly across oceans. However the A220 is showing that smaller regional jets, with long range can offer some intressting options. However that is a jet.

That being said technically it is possible. Practically it is way to expensive.

Completely agree with the greenwashing. Do you think hydrogen would be more dangerous that natural gas? A few years ago there was a lot of fear with gas powered cars but them I never heard of a single one giving issues. Not saying that planes run on natural gas I just feel like it's a similar concern a lot of people have.