Startup seems to be ignored by QSpice in the .trans command

This model is straight off the LM150 datasheet, I’ve verified in LTSpice I see the startup delay if I specify the startup option, in QSpice it behaves the same way with or without the startup option, and doesn’t show the soft start.

HELP in Qspice doesn’t mention about Startup modifier for .tran, may be Qspice not offer this yet.
For your case, replace Startup with UIC (skip initial condition) and should get a close enough result as LTspice with Startup in .tran.

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You can also simulate startup by taking a PWL type source instead of a constant voltage source: V1 Vcc 0 PWL 0 0 10u 20

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