Ok, call me elitist then. But 5g is too small for a male betta for an extended period of time. 10g should be the bare minimum long term home for them and a 20g long is preferable.

They are territorial and explore and swim around a lot and 5g just does not give them enough space to do that.

2 meters is 6 feet.

Its way bigger than what a betta would need. 5g I would argue is still too small. 10 or 20 is what I prefer. My two bettas are in 20 gallons. 6 feet is like a 100 gallons easily and is overkill. Bettas are obligate air breathers also so they dont necessarily like really tall tanks. A 20g long might be better than a tall 30g because of less height and more surface area.

The myth that they can survive in 5, 2,1 gallons, or crayon boxes or mason jars, or wine glasses is that they exist in puddles in canals, floodplains, and rice paddies. But that is still abuse in a home setting.