According to the ECtHR Information Note:

This case concerned the impossibility for the applicant, a Guinean national, to be heard in immigration detention appeal in person or by tele- or videoconference due to initial infrastructure problems in Covid-19 pandemic. The Court declared the application inadmissible, as being manifestly ill-founded, finding that the applicant had been entitled to take proceedings within the meaning of Article 5 § 4 (right to a speedy decision on the lawfulness of detention) of the Convention and that in the circumstances of the present case those proceedings met the requirements of that provision. The Court noted in particular that, given the difficult and unforeseen practical problems with which the State had been confronted during the first weeks of the Covid-19 pandemic, the fact that the applicant had benefitted from adversarial proceedings during which he had been represented by and heard through his lawyer who had attended the hearing by telephone and with whom he had had regular contact, the importance of the applicant’s other applicable fundamental rights and the general interest of public health, the examination of the detention order without securing his attendance at the hearing in person or by videoconference had not been incompatible with Article 5 § 4.