I thought you might like to see what your plant will eventually do. This is one of mine. It is over 20 years old. I don't take care of it, never fertilize it, the only water it gets is rain. Its in full sun all day every day by the pool.
You can see the diameter of the roots it has.
These are what anchor the plant upright as the trunk grows.
These roots will also attach to things if there is something to attach to, like a tree, or a wall.
Selloum is one of the Meconostigma philodendrons. There are 2 basic divisions of the Genus Philodendron, Philodendron and the sub-genus Meconostigma. The Meconostigmas have been reclassified into a new genus of their own, Thaumatophyllum. But this is controversial. If you would like to know more google Thaumatophyllum or Meconostigma.
The Thaumatophyllums all have as their most distinguishing feature the trunk and the eyes on the trunk where the old leaves fall off and leave eye scars. They are also usually pinnate as opposed to entire-leaf plants. Xanadu is one, EVansii is another there are 7-8 and there are hybrids like African Fantasy, Atom etc
If my plant was a houseplant, it would have to be in nothing less than a 35 gallon container. Possibly even a 50 gallon tub.
It will take yours a while to get this big, and it will be slower because it is containerized inside a house. But these can live for decades. Older neighborhoods here have them that are at least 50-60 years old. Some houses have then as 8-9 ft privacy hedges.