Yes, because a long rest requires sleep.
PHB 186 (errata'ed):
A long rest is a period
of extended downtime, at least 8 hours
long, during which a character sleeps for
at least 6 hours and performs no more
than 2 hours of light activity, such as reading,
talking, eating, or standing watch.
If an elf meditates during a long rest (as described
in the Trance trait), the elf finishes the rest after only 4
hours. A meditating elf otherwise follows all the rules for
a long rest; only the duration is changed.
Because a character must be asleep for 6 hours (or, if they are elves, trancing for 4 hours), they cannot do anything else.
As for your specific examples, the revised ranger UA specifies that summoning an animal is work:
With 8 hours of work and the expenditure of 50 gp worth of rare herbs and fine food, you call forth an animal from the wilderness...
Given that it's explicitly described as work, it is incompatible with a long rest.
PHB 114 specifies that a wizard takes only a few minutes to change out their spells:
Preparing a new list of wizard spells requires time spent studying your spellbook and memorizing the incantations and gestures you must make to cast the spell: at least 1 minute per spell level for each spell on your list.
Which is consistent with the "no more than 2 hours" of light activity requirement.
Finally, copying a spell scroll might fall into the light activity category, given that it's mostly reading and writing, but you obviously cannot copy a spell scroll while asleep, so you can't spend an entire long rest copying a spell scroll.