I play bass guitar and would like to learn to play the upright. Can I learn on an electric upright first?
There is no simple answer that would encompass all individuals, but there are some general consideration about learning first on an electric upright bass. There may be something that restricts you from starting on a regular (acoustic) upright bass, so if that is the case, yes you can learn on the electric upright first until the opportunity to play a regular upright bass is possible for you.
If you learn on an electric upright, keep in mind that there will be adjustments that you will need to make, if and when you decide to play the acoustic. Since the electric upright bass has virtually no body, you can conceivably stand as close to the instrument’s strings as you would ever want. You can buy a bass that has some “props” that mimic where the upper bout would be, but it’s still not the same as getting used to playing with a bass’ body keeping you a certain distance from the strings.
The acoustic nature of the upright bass is what makes the tone so rewarding and also unforgiving. Good electric upright basses are responsive to changes in articulation, but no where near the level of an acoustic upright bass. An upright bass has a very expansive palette, which is what makes it harder than an electric upright bass or bass guitar to play consistently, but it also allows you a lot of flexibility through variations in technique which for expressiveness when you get to a higher ability. The same techniques used on an electric upright bass often times does not produce a desirable tone. This is the same reason that a lot of upright bassists complain that electric upright basses are not expressive, electric upright basses don’t sound good when you deviate to far from the sweet spot.
Most electric upright basses sound lousy when playing arco (with a bow), so you won’t be able to develop your bowing technique. A lot of bass guitar players mention that they have no interest in learning to play with a bow, so this may not be an important factor to you. I would highly encourage you to learn to be competent at playing with a bow, because it’ll make you a far better bassist in the long run.