Can I build a fond with seitan?
Yes*
*However, you may find the results from using seitan only disappointing.
In my trials so far, I was able to build a fond with seitan. It tasted primarily of toasted bread, and burned easily. While my memories of other fond-forming foods (meat, alliums, mushrooms) are hazy, I am pretty sure that they produced more fond and had more complex flavors in practice.
Experiment Details
Materials
All described experiments were run using the same commercially-prepared seitan product (Outdated US text data here, official site here) in all trials.
Factors specific to this product that may differ from seitan made at home or by other brands:

The oil present in the prepared seitan may influence fond formation
Flavorings (kombu, soy sauce) may make significant contributions to savory flavors
Other recipes may have additional, fond-forming carbohydrates (added sugar, onion and other aromatics, etc.)

One 8 oz pacakge was used per trial.
Results
For the first trial, I tried browning large pieces in a single batch. Most of the seitan did not stick to the pan at all, lifting easily even after considerable amounts of time (~1 minute) left unattended. Only a small amount of fond formed in the center of the pan, where most sticking occurred. The fond was cooked until quite dark. After deglazing and reducing, the result was a few teaspoons of smoky and charred liquid with a significant savory component.
For the second trial, the seitan was first chopped into smaller pieces (about 0.5cm x 0.5cm x 1cm) before browning. As before, all pieces were cooked in a single batch. Less oil was added to the pan, and there was more sticking in this trial. More fond seemed to form, again primarly in places where the seitan pieces stuck to the pan. The fond was cooked to a lighter color than it was in the firsts trial, and the result of deglazing and reducing was primarily savory with burnt and smoky components.
For the third trial, the seitan was chopped into smaller pieces before cooking. In this trial, a two-batch approach was attempted. The behavior of the first batch was similar to the behavior observed in the second trial. The fond left in the pan by the first batch seemed to develop undesired charred flavors despite the addition of the relatively moist fond of the second batch.
Additional Comments
It seems that seitan does not release that much water when pan-fried, and the water it does release is not enough to re-integrate fond with unbrowned seitan. You may get better results by finely chopping, shredding, or grinding the seitan and browning as much as possible in a single batch.
Aside: &quot;[sticking] to the bottom [instead of] creating a good fond&quot;
In my personal experience with seitan (and other foods), &quot;sticking to the bottom&quot; is highly correlated with fond production. This correlation was most dramatic when cooking larger pieces of seitan; large pieces that did stick (usually in areas with less oil) would leave fond in the pan, while pieces that did not stick would crisp up but leave no perceptible amount of fond.
While I was unable to find a single authoritative source that outright claims that fond is solely or primarily produced by food sticking to a pan, many sources appear to be consistent with that claim. Selected quotes from articles:
Serious Eats

All the tasty browned bits left behind after searing meat are called fond...
Because I want to encrust the bottom of the pan with a golden crackly fond...

The Kitchn

In both cases, small particles of the food being cooked will stick to the bottom of the pan ... This is what is called the fond.

Cooking for Engineers

Fond is the highly flavorful, browned bits of meat stuck to the bottom of a pan after sautéing.