They can't hybridize.
Animals and plants have multiple chromosomes, and they have two of each one, so you can make an hybrid that mix some chromosomes of one variant with the chromosome of other. [Actually, plants are even more weird.] [And there is crossover, that mix the chromosome of the parents.]
The covirus have only one strand of RNA, so you can't mix it with another strand of another variant From https://en.wikipedia.org/wiki/Coronavirus#Genome
> Coronaviruses contain a positive-sense, single-stranded RNA genome. The genome size for coronaviruses ranges from 26.4 to 31.7 kilobases. The genome size is one of the largest among RNA viruses. The genome has a 5′ methylated cap and a 3′ polyadenylated tail.
This is different than the flu virus, that have multiple pieces of RNA (each one is different), so you can mix variants. From https://en.wikipedia.org/wiki/Influenza#Structure,_propertie...
> The central core contains the viral RNA genome and other viral proteins that package and protect this RNA. RNA tends to be single stranded but in special cases it is double. Unusually for a virus, its genome is not a single piece of nucleic acid; instead, it contains seven or eight pieces of segmented negative-sense RNA, each piece of RNA containing either one or two genes, which code for a gene product (protein).
