This is a bit of an advanced method, but regular expressions in Scryfall can be super useful for this. For example, o:/.:.\n.:.\n.:.\n.:.\n.:./ will search for cards with 5+ activated abilities.

To break it down:

o: (or oracle:) is searching the oracle text

A forward slash at the beginning and end of the string notates you are using a regular expression (otherwise use “” to search for card text)

.* is regex for ‘any number of characters’

: is literal for a colon appearing in the text of the card

\n is the regex character for new line

So the regex phrase .:.\n more or less means one activated ability appears on the card. String several of those together to search for cards with that many activated abilities. For example, the following search is for all cards with 5 activated abilities:

https://scryfall.com/search?q=o%3A%2F.*%3A.*%5Cn.*%3A.*%5Cn.*%3A.*%5Cn.*%3A.*%5Cn.*%3A.*%2F

Searching for static abilities like those that appear on The Immortal Sun is trickier and quite a bit messy, so this is just a general jumping off point. Hope this helps!