In a nutshell, we showed that over-the-counter cheap generic antibiotic neomycin can be repurposed in nasal formulation to prevent & treat infection, block transmission, and reduce disease burden against a wide array of viruses. Since this is a host-directed strategy and virus-agnostic, it holds promise as a prophylactic strategy against any viral threat.
The advice in the screencapped thread was to apply a little with a q-tip to the inside of the nostrils.
There is no info on any dangers of doing this very often, but if you can't avoid a high-risk environment it's worth trying.
Here's a thread about the study. https://threadreaderapp.com/thread/1782535781338222960.html
here's the study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5918160/
It doesn't sound like you need to coat the inside of your nose, just put enough to trigger an immune reaction, so I would guess occasional use wouldn't destroy your nasal biome. Plain neomycin without the petroleum jelly should work the same, if you want to avoid petroleum jelly.
This needs more study to measure exactly how effective it is, but the one of the researchers doing the study, Prof Akiko Iwasaki, is a highly regarded immunobiologist.