Use this program:
https://www.redgiant.com/products/instant-4k/
I used it on all our old SD scenes and brought them up to HD
Here is an example...check out the vid trailer. Originally shot at 720 x 480
https://claudia-marie.com/tour/updat...le-dipped.html
That trailer is a 1280 x 720 that was output by Instant 4K
And yes it can put them out at 1080 and even 4K
I chose 720P because that is a good resolution to stream at.
It takes a lot of time to encode each vid out. I spent a couple of months doing all of our old ones 1 at a time.
But it was worth it.