I performed a PubMed search on COVID-19 and laryngitis as well as COVID-19 and Voice.
I found 9 good articles on this topic which definitely conclude that voice changes can be a result of COVID-19. Here are a few of the citations.

Kimura, Y.; Hirabayashi, E.; Yano, M.; Fujitani, S.; Shioiri, S. COVID-19 Omicron variant-induced laryngitis. Auris Nasus Larynx 2023, 50, 637-640, doi:10.1016/j.anl.2022.08.007.

Aghadoost, S.; Molazeinal, Y.; Khoddami, S.M.; Shokuhifar, G.; Dabirmoghaddam, P.; Saffari, M. Dysphonia Severity Index and Consensus Auditory-Perceptual Evaluation of Voice Outcomes, and Their Relation in Hospitalized Patients with COVID-19. J Voice 2022, doi:10.1016/j.jvoice.2022.11.034.

Yasien, D.G.; Hassan, E.S.; Mohamed, H.A. Phonatory function and characteristics of voice in recovering COVID-19 survivors. Eur Arch Otorhinolaryngol 2022, 279, 4485-4490, doi:10.1007/s00405-022-07419-2.

Romero Arias, T.; Betancort Montesinos, M. Voice Sequelae Following Recovery From COVID-19. J Voice 2022, doi:10.1016/j.jvoice.2022.06.033.

Khoddami, S.M.; Aghadoost, S.; Aghajanzadeh, M.; Molazeinal, Y. The Health-related Quality of Life and Voice Handicap Index in Recovered COVID-19 Patients in Comparison to Healthy Subjects. J Voice 2023, doi:10.1016/j.jvoice.2023.05.003.

I attached the pdfs for you and your MD to review.

Also, make sure you are not on a medication that can effect a voice change. For example, diuretics such as Lasix® and others will cause changes in the vocal cords. Create a list of all your medications & supplements and ensure that none are not the culprits or are adding insult to injury.

One further thought. I wonder if you consulted with a COVID-19 expert before having the Botox injections. I presume the latter were into the muscles near the vocal cords-- yes? I did find this as an adverse affect of Botox injected near the vocal cords:

"The other, more common side effect is that your voice may become weak and breathy for some period of time after the injection. This is because the vocal folds are weak and cannot come together strongly to provide a strong vibration. This is what prevents the spasm."

In other words, Botox is used for spasmodic laryngitis, and if you did not have this then the Botox may have weakened the muscles near the vocal cords to cause the whispery voice you now have. In my medical consulting practice of near 60 years, about half of the problems patients had were physician induced. This is called iatrogenic disease. Remember, all medical students are taught over and over that:
Primum Non Nocere or First (above all) Do No Harm .

I suggest you find an expert ENT MD. A good start would be the Mayo in Rochester MN.
I have no affiliation with the Mayo Clinic.
Stephen B. Strum, MD, FACP