PlantUML is also able to generate Gantt. You can test it at: https://www.planttext.com

Above are all available elements I found in PlantUML to build gantts.

@startgantt
Project starts the 5th of august 2019
saturday are closed
sunday are closed
2019/08/15 is closed
[Prototype designx] as [TASK1] lasts 6 days
[TASK1] is colored in Lavender/LightBlue
[Prototype design] lasts 13 days
[Prototype completed] happens at [Prototype design]'s end
[Test prototype] lasts 14 days
[Test prototype] starts at [Prototype design]'s end
[Prototype design] is colored in Fuchsia/FireBrick
[Test prototype] is colored in GreenYellow/FF0000
[Ein Vorgang] starts at [Prototype designx]'s end
[Ein Vorgang] lasts 5 days
[Ein Vorgang2] starts at 15th of august 2019
[Ein Vorgang2] lasts 7 days
[Ein Vorgang3] starts at [Ein Vorgang2]'s end
[Ein Vorgang3] lasts 5 days
[Ein Vorgang4] lasts 9 days
[Ein Vorgang5] lasts 6 days
[Ein Vorgang4] starts at 2019/08/17
[Ein Vorgang5] starts 5 days after [Ein Vorgang2]'s start
[Task1] on {Alice} lasts 10 days
[Task2] on {Bob:50%} lasts 2 days
then [Task3] on {Alice:25%} lasts 1 days
@endgantt