disclaimer: I'm not a nutritionist and have no background in it.
with my son (6'2"/180), me was struggling to get and keep weight. always has. he eats massive amounts but tends to only eat 3x/day. i started him eating a little more often and it seems to have worked. it's tough, though, bc his diet and body aren't exactly programmed that way.
currently, he's still at online school. he had dipped down to 172 following oral surgery (wisdom tooth extraction does not play nicely with trying to gain weight). he starts at 9, goes to noon, lunch until 1230, school until 2. after that, he lifts in the garage, does homework, then either does skills work or practice. dinner is in there, depending on practice time.
he wakes up at 730 and i've gotten him to immediately eat a banana and drink a glass of milk. then he does his morning routine (why does a 15 year old feel compelled to shower before a zoom call???) and eats breakfast (usually leftovers from dinner last night). between his first and second class, he eats a gatorade protein bar. lunch at 1230 (more leftovers). snack or shake after class is over. then a pre-workout drink. shake after lifting, dinner. shake before bed.
with this eating schedule, he's eating a little less volume at each meal but only by slightly. he also (just my observation) spending less time "getting rid of" excess calories via the plumbing. my theory is the body can't handle too many calories at one time so it rids itself of them. by spacing out the calories more, he's more efficient in absorbing them. again, not a dietician/nutritionist/doctor.
in the past month since surgery, he's up to 183. hopefully he can hold it and keep up his eating schedule.