"No filter" is easy - for me anyway.
Here is a desktop "Walstad" dirted 2 gallon planted betta bowl sitting right here next to me.
You don't need a filter on any properly set up planted aquarium - it's surprising how few people around here realize that.
ESPECIALLY in a small tank like this.
"No filter" is a misnomer anyway, and I'm tired of reading that term on a planted tank forum of all places.
Plants are a filter
, they utilizes the waste products you're trying to remove with filtration.
I use a little duckweed in this bowl to pick up the slack of the slower growing Crypts.
Duckweed and water lettuce are fantastic processors of organic waste.
I have a HOB on my 40 gallon, but just for water circulation and to hold the Purigen which removes the tanins from the wood.
A filter is useful to achieve clearer water, and less of that "natural" look, but but they are far from a necessity, and a tank without
one, especially a small/nano tank is simple indeed if that is your wish.
This betta bowl does have a small heater - bettas like warm water.
It requires almost zero maintenance. A 3 minute water change every few weeks.