If you wake without ever feeling refreshed from sleep, no longer remember any dreams, if you snore loudly, if you or a partner notice odd breathing noise or periods when you stop breathing, it’s worth asking your doctor for a sleep apnea test.
It is estimated 70% of stroke survivors will develop sleep apnea. That figure might be skewed by the age of stroke survivors, people are more likely to have sleep apnea the older they get.

The chances of you developing this post stroke are much higher than the general population. On that basis, it should surely form part of a checklist for items to monitor in hospital or at home ?

There seem to be 3 ways in achieving a diagnosis. The first is a simple questionnaire.
Secondly if your answers suggest more investigation is needed, then the investigation can take place in two ways

invited to spend a night in hospital where you are monitored
at home where you will wear a device on your head and a sensor on one finger.

Everyone stops breathing at times during the night, up to 5 times an hour is considered normal.
If it gets above this figure, the solution is either

a mouth guard to help keep the airways open. This is often considered the second best solution.
A cpap machine. This pumps pressurised air via a face mask to help reduce the number of times your airways close. This can be nasal only, mouth and nose or more of a fuller face mask.
You may have to try a number of masks to find one that is suitable. Keep a look out for any pressure sores.
You might find, if you can tolerate the mask and machine that you feel much more alert in the day and your need for as much sleep reduces.
You can see the results on the machine and often via an App.

An apnea is an event when you stop breathing. After a very short while, your brain is on high alert looking for a solution asap. You might not wake up at this point but your brain has. This disrupts the sleep patterns and you might not enter any deep sleep. Smart watches might indicate sleep stages but they are an estimate, not fully reliable.

There are two types of apneas

obstructive when your windpipe closes
central when your brain does not send a signal to initiate a breath.
Obstructive is by far the most common. It is possible to have both and some machines can show both types in their report data.

Feeling tired post stroke is normal. However it might be that the stroke is not the only cause of the fatigue.
Lots of but very poor quality sleep will not help much.